The incidence of surgical treatment for temporomandibular joint internal derangement is increasing in the U.S. The criteria used for selecting surgical candidates identifies patients with non- reducing anterior dislocated discs or severely damaged discs as those most responsive to surgical correction of temporomandibular joint (TMJ) internal derangements. When a meniscectomy is performed, the surgeon requires an interpositional material to prevent bone to bone contact between the condylar head and bony glenoid fossa and subsequent degenerative changes. Materials currently used by clinicians include Proplast-polymer laminates, silicone rubber, lyophilized dura, or dermis grafts. The advantages (i.e. tissue ingrowth, biocompatability, fibrous tissue replacement or metaplasia) and disadvantages (i.e. slippage, foreign body reaction, lack of strength) of these materials have not been directly compared in an objective and appropriate animal model. In order to compare interpositional materials that are commonly used and represent the two predominant reconstructive philosophies for meniscectomy patients, a glenoid fossa resurfacing material (Proplastpolymer) or a meniscus substitute will be used to examine these philosophically different reconstructive modalities. Fifteen Macaca fascicularis monkeys will undergo unilateral TMJ meniscectomy. Either a Proplast- polymer laminate, a dermis graft, or no replacement (control) will be inserted. The animal will receive the implants on only the left TMJ. Unilateral surgery will enable examination of one TMJ without contributions from the opposite TMJ. In addition the unoperated joint will be used to determine the effect of unilateral surgery on the unoperated contralateral, TMJ. Four months after surgery the animals will be sacrificed for clinical, radiographic and histologic evaluation. The results of this pilot study should provide sufficient information for preparation of a larger study.